# US 11,906,738 B2 · Scanning MEMS mirror angle-doubling using polarization > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,738 B2 - Document ID: US11906738B2 - Status: Granted - Kind: B2 - Application number: 17/204,457 - Filed: 2021-03-17 - Published: 2022-09-22 - Granted: 2024-02-20 - Earliest claimed: 2021-03-17 - Assignees: Google Inc. - Applicants: Google LLC - Inventors: Daniel Adema - Web page: https://patentgrep.com/patent/US11906738B2 ## CPC - G02B 27/0172: {characterised by optical features} - G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)} - G02B 17/004: {Systems comprising a plurality of reflections between two or more surfaces, e.g. cells, resonators (multipass arrangements for optical cuvettes G01N21/031; laser resonators H01S3/05)} - G02B 26/0833: {the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B)} - G02B 26/10: Scanning systems - G02B 26/105: {with one or more pivoting mirrors or galvano-mirrors (G02B26/101 takes precedence)} - G02B 27/0018: {with means for preventing ghost images (anti-reflection coatings G02B1/11)} - G02B 27/283: {used for beam splitting or combining} - G02C 11/10: {Electronic devices other than hearing aids} - G02B 2027/0123: {comprising devices increasing the field of view} - G02B 2027/0178: {Eyeglass type (eyeglass details G02C)} - G02C 5/22: Hinges (pivotal connection in general F16C11/00) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G02C: SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES (trial frames for testing the eyes A61B3/04; goggles or eyeshields not having the same features as spectacles A61F9/00) ## Abstract Systems and methods for manipulation of the polarization state of light emitted by a laser projector to reduce the angle range of a scanning mirror articulated by a micro-electromechanical system MEMS to reduce power consumption are disclosed. A system includes a light source configured to emit laser light, a scanning mirror, and an angle expander disposed between the light source and the scanning mirror, the angle expander being configured to cause the laser light from the light source to be reflected at least once from the angle expander and at least twice from the scanning mirror. ## Claims ### Claim 1 An apparatus comprising: a light source configured to emit laser light; a scanning mirror; and an angle expander disposed between the light source and the scanning mirror, wherein the angle expander is configured to cause the laser light from the light source to be reflected at least once from the angle expander and at least twice from the scanning mirror. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the angle expander comprises; a polarization beam splitter (PBS); and a quarter-wave plate (QWP). ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the PBS is configured to reflect laser light having a first polarization and to transmit laser light having a second polarization. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the light source is configured to emit laser light having the first polarization. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the scanning mirror is a micro-electromechanical system (MEMS) based scanning mirror. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the angle expander is positioned at a non-zero angle relative to a rotational axis of the scanning mirror. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the scanning mirror is enclosed in a vacuum-sealed enclosure and wherein the angle expander is configured as a window of the vacuum-sealed enclosure. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the apparatus is a wearable heads-up display (WHUD). ### Claim 9 A method comprising: emitting, from a laser light source, laser light having a first linear polarization towards an angle expander; transmitting the laser light having the first linear polarization through the angle expander disposed between the laser light source and a scanning mirror, the angle expander comprising a polarization beam splitter (PBS) and a quarter-wave plate (QWP), wherein the QWP is disposed between the PBS and scanning mirror; reflecting for a first time, at the scanning mirror, laser light transmitted from the angle expander; reflecting, at the PBS, the laser light reflected from the scanning mirror; reflecting for a second time from the scanning mirror, the laser light reflected from the PBS; and transmitting, through the PBS, the laser light reflected from the scanning mirror. ### Claim 10 (depends on 9) The method of claim 9, wherein the PBS is configured to transmit laser light having a first linear polarization and to reflect laser light having a second linear polarization. ### Claim 11 (depends on 10) The method of claim 10, further comprising: converting the laser light reflected for the first time from the scanning mirror to laser light having the second linear polarization on incident with the QWP. ### Claim 12 (depends on 10) The method of claim 10, further comprising: converting the laser light reflected for the second time from the scanning mirror to laser light having the first linear polarization on incident with the QWP. ### Claim 13 A laser projector system comprising: an optical engine configured to emit laser light along a path; a scanning mirror configured to reflect the laser light; a polarization beam splitter (PBS), disposed in the path of the laser light between the optical engine and the scanning mirror, the PBS being configured to selectively reflect laser light based on a polarization state of the laser light; and a quarter-wave plate (QWP), disposed in the path of the laser light between the scanning mirror and the PBS, wherein the PBS is positioned at a non-zero angle relative to a rotational axis of the scanning mirror. ### Claim 14 (depends on 13) The laser projector system of claim 13, wherein the optical engine is configured to emit laser light having a first polarization state. ### Claim 15 (depends on 14) The laser projector system of claim 14, wherein the PBS is configured to transmit laser light having the first polarization state and to reflect light having a second polarization state. ### Claim 16 (depends on 15) The laser projector system of claim 15, wherein the scanning mirror is a micro-electromechanical system (MEMS) based scanning mirror. ### Claim 17 (depends on 13) The laser projector system of claim 13, wherein the scanning mirror is enclosed in a vacuum-sealed enclosure and wherein the PBS is configured as a window of the vacuum-sealed enclosure. ### Claim 18 (depends on 13) The laser projector system of claim 13, wherein the scanning mirror is enclosed in a vacuum-sealed enclosure and wherein the PBS is configured as a window of the vacuum-sealed enclosure. ### Claim 19 (depends on 13) The laser projector system of claim 13, wherein the scanning mirror is enclosed in an enclosure filled with at least one of a noble gas and nitrogen, wherein the PBS is configured as a window of the enclosure.